In sludge handling systems, it is known to provide treated sewage sludge to bins, in which the sludge resides until it is desired to discharge sludge from the bins. Generally, one or more bins are provided, and the sludge is delivered into the bins at upper ends thereof, and is discharged from the bins through a discharge opening at a lower end of the bin. Generally, the discharge opening is closed until it is desired to discharge from the bin, and at that point, an openable closure is activated, opening the discharge opening at the bottom of the bin, to allow sewage sludge in the bin to be discharged from the bin, generally onto the bed of a waiting truck disposed therebeneath, with the sludge then being delivered to be used as agricultural ground cover, landfill, or the like, as may be desired.
Sometimes sludge resides in the bin for a day or more, such that it may be become increasingly compacted, with sludge along side wall(s) of the bin becoming adhered to the side wall(s), such that when the discharge gate is opened, sludge may not readily flow outwardly of the bin, via gravity flow, also called mass flow, without some assist. This can particularly occur, as the volume of sludge in the bin decreases, because the lower volume, or “head” results in a reduced weight or pressure condition. As the “head” thus decreases, the resistance to flow increases, as sludge tends to adhere to the walls.
Often, a bin in which sewage sludge is handled may have sloped side wall(s) at the lower end of the bin, leading toward a discharge opening. Sometimes, bridging can occur with sewage sludge at the bottom of a bin, in which the pressure of sewage sludge in the bin creates a dome or arch effect above the bin discharge opening.
One approach that has been used to minimize or obviate such doming or arching, or aggregation of sludge at the bottom of a bin, is to provide a rotationally driven discharge arm, that may be of plow-like construction, to sweep across a bottom floor of the bin, pushing sewage sludge along the bottom floor of the bin toward a central opening. Such a discharge arm will generally be motor driven, either by constant speed or variable speed, and will undercut sewage sludge that may have become compacted during the time that it has been in the bin.
Such devices as these that move a discharge arm across a generally horizontal surface at the bottom of a bin, can be effective in many situations.
However, the longer a bin has been in use, the interior surfaces of the side wall(s) of the bin can become rough due to rusting, or due to other phenomena, such that sewage sludge may not slide easily along sloped surfaces of the bin, downwardly toward a discharge opening, but, rather, may accumulate on sloped surfaces of the bin.